1. Field of Invention
Warning lights are commonly used on automotive vehicles such as school busses to provide a highly visible visual warning means. Performance criteria for school bus signal lamps have been standardized by the SAE through its published standard SAE J887. School bus signal lamps are alternately flashing lamps which are mounted horizontally both front and rear and intended to identify a vehicle as a school bus while informing other users of a highway that a vehicle is stopped on a highway in order to discharge school children. The SAE has promulgated standards which warning lights such as those used on school busses must meet, among them are vibration tests, moisture tests, dust tests and corrosion tests for the entire assembly.
Of the tests required, one of the most stringent are the photometric tests which must be performed pursuant to J of SAE J575. In order to assure that the effective projected illuminated area when measured on a plane at right angles to the axis of the lamp will be not less than 19 square inches, the juxtapositioning of the sealed light bulb within the housing and lens superstructure must be accurately maintained. Any aiming of the warning light assemblies done through external aiming pads on the outer surface of the lens which are suitable for use with a mechanical head lamp aimer.
Because of these voluntary standards, which have in many cases been adopted or expanded upon by state regulatory authorities to cover the performance characteristics of warning lights, particularly for school busses, there has existed a need for a unitary assembly which economically and reliably ensures specification requirements.
2. Description of the Prior Art
Exemplary of a common type of mounting for a warning light such as required in a school bus warning light assembly is that illustrated in FIG. 1, and labeled as prior art. According to this conventional assembly there is a housing which is invariably metallic with an opening 14 for the projecting connectors of the general service sealed light. In order to hold the sealed light unit 12 securely within the housing, the prior art has commonly employed discrete and separate bulb hold down brackets 6 which are required to be manually applied over the retaining flange of the sealed light bulb with separate fasteners 8.
At this point, it is pertinent to note that the general service sealed light illustrated at 12 in FIG. 1 is also illustrated in an embodiment according to the present invention at FIG. 3 and reference will be made to FIG. 3 for purposes of explaining further considerations dictating the only approved manner of mounting a sealed light bulb. General service sealed lighting units are themselves the subject of a SAE standard. According to the SAE recommended practice, as delineated in SAE J760, a sealed lamp 12 includes a lamp seal 33 which includes an annular bulb retaining flange 34 on an upper surface and further includes a lower lamp edge seal 37 which is spaced outwardly from a further seating plane which is defined with an edge 35. The lamp seal 33 itself will vary in contour and thickness and should in no case be used for seating and holding purposes. The lamp itself must be held between the seating plane 35 and the retainer flange 34 without reliance upon the particular contour of the lamp seal 33 itself. The lamp seal as defined between surfaces 34 and 37 itself includes a manufacturing tolerance of .+-.0.040 inches. To compound the dimensional problems, the outermost diameter of the seal 33 is, for a 53/4 inch diameter sealed lighting unit, nominally 5.700 .+-. .100 inches.
The lamp seal is not itself an allowable mounting surface and its tenth of an inch diameter tolerance, taken together with its allowed configuration contour, creates an alignment problem for any mounting system that is to be contemplated.
As illustrated at FIG. 1 the seating plane of the bulb is normally placed in contact with the metallic housing 4 with the provision of a gasket 16 relied upon for sealing the lamp housing itself against intrusion of water and dust from the interface of the lens and the housing 4. Such a gasket 16 normally abuts against the seal 33 and is relied upon to prevent water from seeping in from the elements around the lens. In the manufacturing process a manual assembly of the bulb 12 with manual positioning of the bulb against the seating rim of the housing ensured only by a worker using the individual brackets 6 and tightening them with separate bulb hold down screw 8. A second manufacturing assembly step is positioning the lens to with hold down screws 10 extending through a series of bosses which have to be lined up with openings found drilled through the metal housing flange. Finally, other bosses are provided with holes for mounting screws 18 which extend through further bosses and holes within the metal housing and are adaptable to be secured into the sheet metal of the vehicle body. In the final application the sealed beam electrical connections 20 are exposed through an opening or housing access as illustrated at 14 and require electrical connection to be made during mechanical placement of the assembly on the vehicle body, with the attendant likelihood of damage to the electrical connectors 20 from an inadvertent contact with part of the vehicle.